Scuba Math

Broad Question: What pressure group am I after my second scuba dive of the day?

Focused Questions:I went to 35 feet for 30 minutes on my first dive and 87 feet for 20 minutes on my second dive. What is my pressure group?

Answer: Group after first dive is D, after surface interval is C.

I went to 15 feet for 40 minutes on my first dive and 57 feet for 10 minutes on my second dive. What is my pressure group?

Answer: Dive group after the first dive is E, after the surface interval is D

Process and Tools:To answer these focusing questions I used an online electronic dive table. I put in the values for how deep each dive was, how long I stayed at depth, and how long the surface interval was between each dive. For these questions I used a default surface interval of an hour and a half, as that is what is typically done. I then calculated these values together to determine my pressure group prior to a third dive.

Expanded Explanation and Process:When scuba diving you get nitrogen in your blood. The deeper you go, the more nitrogen enters your blood. Because of this you have to be careful with how deep you dive when doing multiple dives in one day, as residual nitrogen remains in your system from previous dives. Dive tables and computers measure approximately how much nitrogen should be in your blood based how how deep you were and for how long, and they use this information to tell you how much nitrogen you can still take without getting sick- usually defined in a pressure group that is represented by a letter.

New Elements in Focused Questions: For these I played with different surface intervals- you can see how drastically this effected the results.How deep can I go on my third dive of the day if I was at 80 feet for 30 minutes, had a three hour surface interval, and then was at 60 feet for 20 minutes?

Answer: Dive group after first dive is R, after surface interval is A

How deep can I go on my third dive of the day if I was at 20 feet for 20 minutes, had a one hour surface interval, and then was at 20 feet for 20 minutes again?

Answer: Dive group after first dive is C, after the surface interval is C

The image below is a dive table. I put the steps to answering one of the original focused questions in yellow, and to answering one of the in depth ones in green. The arrows show the order of the steps.